Supplying of electromagnetic clutches of vehicles



1967 G. DE COYE .DE CASTELET 3,335,82

SUPPLYING OF ELECTROMAGNETIC CLUTCHES OF VEHICLES I Filed Oct. 23, 1965 v 60?): Buoy: orcnsrzus-r HTToRNE Ys INVENTOR v United States Patent 3,335,829 SUPPLYING OF ELECTROMAGNETIC CLUTCHES 0F VEHICLES Ga'eltan de Coye de Castelet, Billancourt, France, assignor to Regie Nationale des Usiues Renault, Billancourt, Seine, France Filed Oct. 23, 1965, Ser. No. 503,009 Claims priority, application France, Jan. 9, 1965, 1,402, Patent 1,433,388 2 Claims. (Cl. 192-.033)

approximately from as much again to double, i.e. the

regulation of the electrical supply is a poor compromise between easy operation in the cold state and safety in the hot state, more particularly when it is the speed of the engine which wholly or partly regulates the intensity used in clutch engagement.

Other factors come into play to further reduce the torque which can be transmitted in the hot state, more particularly approach of some or all of the materials of the magnetic circuit to the Curie point, a phenomenon noticeable in powder couplings.

Clutches of the size used in vehicles are not well suited to the usual compensation of the coil resistances by series connection of resistances having a negative temperature coefficient since, on the one hand, the powers in question are considerable, and on the other hand, space is restricted in these clutches. Finally, the supplying of clutches with direct current by regulating devices having a high internal resistance comes up against thermal problems which limit the use thereof to low powers.

The present invention relates to a method of and an apparatus for compensating for the heating of these clutches by means of a resistance having a high positive temperature coefficient placed in thermal contact with the clutch and acting on a control circuit of the clutch coil. Since the energy to be controlled is very slight, the resistance is very small and easy to arrange.

Since this resistance can also be connected in parallel with the synchronization contact between engine and gear box which electromagnetic clutches usually possess, there is no modification to the wiring outside the clutch nor to the number of supply brushes.

The invention will now be described with reference to the accompanying drawings illustrating one example of embodiment, in a case where the current in the clutch is regulated by the speed of the engine.

FIGURE 1 shows the electrical connection diagram of an apparatus according to the invention;

FIGURE 2 is a simplified sectional View of an electromagnetic powder clutch with its brushes and its compensatin resistance;

FIGURE 3 shows the evolution, as a function of time, of the voltage at a point of the diagram shown in FIG- URE 1 subjected to the action of the compensating resistance;

FIGURE 4 shows the pattern of the characteristic curve of the resistance or resistances used as a function of temperature;

FIGURE 5 shows the arrangement of a compensating 3 ,335,829 Patented Aug. 15, 1967 "ice network composed of ordinary resistances and resistances having a high positive coefficient;

FIGURE 6 shows the pattern of the intensity characteristic of the current passing through the clutch as a function of the speed of the engine at the time of starting;

FIGURE 7 shows, as a function of the coil resistance, the curve of the speed of the engine corresponding to equilibrium between the engine torque and the torque transmitted by the clutch. This speed is substantially that assumed by the engine during a considerable part of a starting operation with the accelerator fully depressed.

In FIGURE 1, given by way of an example of embodiment, there have been shown the essential elements of an electrical supply system of known type, described in the US. Patent No. 3,203,518, of Aug. 31, 1965, for Supply for Electrical Clutches of Vehicles.

It comprises a vehicle battery 1 whose positive output line 2 and negative output line 3 supply the primary 4 of the ignition coil of an interal combustion engine associated with the breaker 5 and with the ignition condenser 6. Interposed upstream of the primary 4 in the positive line 2 is the primary 7 of a transformer 8 comprising two secondary windings 9 and 10. The secondary 10 has a tap connected by a resistance 29 to the line 2. The primary 7 whose current is subjected to the variations caused by the breaker 5, constitutes the engine speed information element of the electronic apparatus 11 for supplying the electric clutch 13 which has a coil 12 and a synchronization contact 14 between the vehicle engine and the gear box input. This contact is open when the speed of the engine is higher than that of the input shaft of the gear box; with the resistance 15, it is arranged at the terminals of the auxiliary winding 10 of the transformer 8 by way of the connection 22 and both, therefore, modify by coupling the voltages which appear at the terminals of the winding 9 at each movement of the breaker 5.

Arranged at the terminals of the secondary winding 9 is a circuit comprising a diode 16 which detects the voltage due to the opening of the breaker 5 and a condenser 17 whose contact, at the diode 16 end, is connected to the negative line 3 through the agency of a resistance 18, the function of which is to discharge the said condenser, Whose charge is due to the voltage of the winding 9 and that of the battery 1.

Arranged at the terminals of the condenser 17 is the supply circuit of the clutch coil 12 which, by way of a voltage/ current amplifier 19, supplies the coil 12 from the battery in dependence on the charge wave amplitude of the condenser \17 by way of the connections 20 and 21.

FIGURE 2 shows a form of embodiment of an electromagnetic powder clutch comprising a coil 12, a contact 14 and a resistance 15 having a positive coeflicientv The driving part 24 of the clutch is fast with the output shaft 23 of the engine and contains the coil 12 which surrounds a bore 24a in which is accommodated a ring 25 fast with the input shaft of the gear box 26; the cavity is filled with a magnetic powder 27 which makes it possible to gradually couple the elements 24 and 25 under the action of the induction developed by the coil 12. Within a cover 24b closing the cavity 24a there is arranged the resistance 15 divided into a resistance having a high positive coefiicient 15a and an ordinary resistance 15b arranged in series, the assembly being in parallel with a contact 14, such that this contact opens when the part 24 rotates faster than the shaft 26. The resistance 15a is in a good thermal contact as possible with the mass 24 and is held in position by a spring 28.

The arrangement which has just been described is of course applicable to other supply apparatus, when it is possible to modify the current impulses supplied to the coil 12 by means of a resistance having a high positive coefiicient arranged in thermal contact with the clutch and acting on a control circuit.

Operation will be explained with reference to FIGURE 3 which shows a voltage oscillogram of the condenser 17. An opening of the breaker 5 causes the charging of the condenser at the voltage U1 at an instant t1, the resistance 18 discharging the condenser completely at the point of time 12. The amplifier 19 is such that it sends current into the clutch between 11 and t2. If the resistance 15 has a small value, some of the energy normally intended for the condenser 17 will be diverted by the winding towards the resistance and the charge voltage will fall to U2, discharge occurring at 13 prior to 12, that is to say each opening of the breaker will send current into the coil during a shorter time than previously. When the engine speed is less than that of the input shaft of the gear box, the contact 14 is closed, short-circuiting the resistance 15 so that in that case the current sent into the coil 12 is very small. On the contrary, when the engine speed is greater, even very slightly greater, than the speed of the gear box input shaft, the contact 14 is opened and the current in the coil 12 is strong and is regulated by the value of the resistance 15 which varies in dependence on the temperature of the clutch. Consequently, the amplifier will send less current for the same speed, the clutch being cold, when the coil has little resistance and the resistance 15 has a lower value than in the hot state when the resistance 15 has a higher value.

In FIGURE 4, the curve 4a represents the variation of resistance R necessary as function of the temperature T. If this characteristic cannot be obtained by a single resistance 15, an approximate curve with two slopes can be used by means of the network shown in FIGURE 5 using resistance 15:21 and 15a2 having respectively a characteristic 4c and 4b associated with ordinary resistances 15131 and 15b2,

These resistances having a high positive coeflicient will usually have a base of relatively poorly conductive materials whose Curie point is within the working zone. Several types exist which can be obtained commercially.

FIGURE 6, which represents the intensity I in the coil 12 at the time of starting, in dependence on the engine speed N, shows the characteristic 6a obtained at the ambient temperature T1. Owing to the higher resistance of the coil at the higher temperature T2 the characteristic 6b would then be obtained. Increasing the resistance 15 under the effect of the temperature makes it possible to obtain the steeper characteristic 6c. The intensity :2 which balances at T2 the engine torque, although higher than that i1 which balances the same torque at T1, will be obtained at a lower engine speed 122 than the speed n1 obtained at T1.

FIGURE 7 illustrates, as a function of the resistance of the coil 12 (which varies with the temperature of the clutch), the speed of the engine corresponding to equilibrium between the torque and the torque which can be transmitted by the clutch, in the case of starting and accelerating with full depression.

The curve 7a corresponds to operating with over-compensation, the curve 7b to operation without compensation by a resistance 15, regulation being moreover returned to equality for the coil resistance r1 by the modi fication of the resistance 18.

The apparatus described is applicable to other known supply apparatus whenever it is possible to modify the signals applied to the clutch 112 in the desired sense by means of a resistance 15 having a high positive coefiicient arranged on the clutch 13 and acting on a control circuit.

I claim:

1. A device for supplying current to a vehicle electromagnetic clutch having a rotatable driving clutch member, a rotatable driven clutch member, and a coil, comprising; an electronic control circuit connected to said coil for controlling current flow through said coil in respouse to the speed of said driving member; contact means positioned between said driving clutch member and said driven clutch member adapted to open when said driving clutch member rotates faster than said driven member; said electronic circuit including a transformer provided with a first secondary winding connected to said coil and a second secondary winding connected to said contact means; and temperature sensitive resistance means connected across said contact means in contact with said electromagnetic clutch for regulating the current flow through said coil in accordance with the temperature of said clutch when said contact means is open.

2. A device as defined in claim 1 including; an engine for motivating said driving member; an ignition system with a direct current source, an ignition coil, and breaker points for supplying ignition current impulses to said engine; said transformer having a primary winding connected in series with said ignition coil; a non-linear amplifier connected between said first secondary winding and said clutch coil; and a diode and a condenser connected to said first secondary winding; said condenser being connected between the inlet terminals of the non-linear amplifier and charged each time the breaker points open.

References Cited UNITED STATES PATENTS 3,090,548 5/1963 Sargant et al. 1922l.5X 3,197,003 7/1965 Yetter 192-2l.5 X 3,250,341 5/1966 Takahashi 192-2l.5 X

MARK NEWMAN, Primary Examiner.

A. T. MCKEON, Examiner. 

1. A DEVICE FOR SUPPLYING CURRENT TO A VEHICLE ELECTROMAGNETIC CLUTCH HAVING A ROTATABLE DRIVING CLUTCH MEMBER, A ROTATABLE DRIVEN CLUTCH MEMBER, AND A COIL, COMPRISING; AN ELECTRONIC CONTROL CIRCUIT CONNECTED TO SAID COIL FOR CONTROLLING CURRENT FLOW THROUGH SAID COIL IN RESPONSE TO THE SPEED OF SAID DRIVNG MEMBER; CONTACT MEANS POSITIONED BETWEEN SAID DRIVING CLUTCH MEMBER AND SAID DRIVEN CLUTCH MEMBER ADAPTED TO OPEN WHEN SAID DRIVING CLUTCH MEMBER ROTATES FASTER THAN SAID DRIVEN MEMBER; SAID ELECTRONIC CIRCUIT INCLUDING A TRANSFORMER PROVIDED WITH A FIRST SECONDARY WINDING CONNECTED TO SAID COIL AND A SECOND SECONDARY WINDING CONNECTED TO SAID CONTACT MEANS; AND TEMPERATURE SENSITIVE RESISTANCE MEANS CONNECTED ACROSS SAID CONTACT MEANS IN CONTACT WITH SAID ELECTROMAGNETIC CLUTCH FOR REGULATING THE CURRENT FLOW THROUGH SAID COIL IN ACCORDANCE WITH THE TEMPERATURE OF SAID CLUTCH WHEN SAID CONTACT MEANS IS OPEN. 